Computer-implemented automated cartridge libraries, such as automated data storage libraries, comprise large numbers of storage slots, also called storage shelves, in which cartridges, such as data storage cartridges, are stored in position to be accessed by robot accessors that access, move and deliver individual cartridges to data storage drives so that data may be read from or written to the cartridges.
Computer-implemented cartridge libraries, even in the lower cost environments, are able to store cartridges assigned to various host systems, arranged as multiple virtual libraries. In one example, the physical library is split up into two or more virtual libraries where each host is notified of the actual element address of its assigned storage slots and data storage drives in its library. Alternatively, the host's virtual library may be arranged to have virtual element addresses such that the library may move a cartridge to a new storage slot, but keep the same host element address (thus not impacting the host). Each host system maintains an inventory of its element addresses for its cartridges. Whether the library has a single host, multiple hosts with actual element addresses, or multiple hosts with virtual element addresses, the library optionally may maintain cartridges in a “vaulted” state which are not reported to any host system. The library may assign a vaulted cartridge to a host when the host asks for a new cartridge.
The computer-implemented cartridge library maintains a physical inventory of the cartridges, and their library element address in the storage slots, and identifies the physical location of each of the storage slots, comprising, for example, the horizontal “X” and vertical “Y” location of the storage slot on a wall of storage slots, so that the robot accessor can be directed to the desired storage slot. The computer-implemented cartridge library also cross references the virtual library addresses used by the hosts, to the library element addresses of the physical cartridges.
Any one host system has an inventory of cartridges of its virtual library and has no information regarding the other virtual libraries.
The rate of access to the physical cartridges varies by the hosts' desire to access the cartridges to read and/or to write data. This may leave some cartridges in position in a storage slot without being accessed. Also, some cartridges may be new to the library, having been manually placed in the library, and which may be accessed in the future.
In certain instances, cartridges that are left in position in storage slots may bond to their storage slots, to the extent that the robot accessor, when it ultimately attempts to access a cartridge that has been left in position, in response to a move command, has difficulty in removing the cartridge from its storage slot. If the move command fails, the host system is unable to access the data of that cartridge.